Apparatus for evacuating and sealing thermoplastic bags

ABSTRACT

A thermoplastic bag evacuating and sealing unit is shown which has an evacuating nozzle for engaging the mouth of the bag. The nozzle generally defines a chamber open at the bottom and tapered to permit the mouth of the bag to be sleeved thereover. The cross-sectional configuration of the nozzle defines an elliptical segment providing an arcute side in opposed facing relationship with a planar side, creating a differential in the width of the opposed facing walls of the bag which cause a wrinkling of the walls when they collapse, upon evacuation, to engage one another. The wrinkles provide air passages for further evacuation of the bag in the lower area surrounding the enclosed food. The unit also has a heater bar disposed below the nozzle and an opposing pressure bar. The heater bar is heated to a sufficient temperature to fuse the thermoplastic sides of the bag together when pressed between the pressure bar and the heater bar. Parting strips of thin heat-transferable stock such as Teflon strips are interposed between each bar and the adjacent facing portion of the bag and are removable with the bag to be peeled therefrom once and fused thermoplastic has cooled sufficiently to regain its cold strength to permit their removal without endangering the seal.

United States Patent [191 Moreland, II et al.

[ Feb. 18, 1975 APPARATUS FOR EVACUATING AND SEALING THERMOPLASTIC BAGS [75] Inventors: William C. Moreland, ll, Export,

Pa; Arie Van Dyck, Henderson, NC.

Westinghouse Electric Corporation, Pittsburgh, Pa.

[73] Assignee:

Primary Examiner-Travis S. McGehee Attorney, Agent, or Firm-F. A. Winans ABSTRACT A thermoplastic bag evacuating and sealing unit is shown which has an evacuating nozzle for engaging the mouth of the bag. The nozzle generally defines a chamber open at the bottom and tapered to permit the mouth of the bag to be sleeved thereover. The crosssectional configuration of the nozzle defines an elliptical segment providing an arcute side in opposed facing relationship with a planar side, creating a differential in the width of the opposedfacing walls of the bag which cause a wrinkling of the walls when they collapse, upon evacuation, to engage one another. The wrinkles provide air passages for further evacuation of the bag in the lower area surrounding the enclosed food. The unit also has a heater bar disposed below the nozzle and an opposing pressure bar, The heater bar is heated to a sufficient temperature to fuse the thermoplastic sides of the bag together when pressed between the pressure bar and the heater bar. Parting strips of thin heat-transferable stock such as Teflon strips are interposed between each bar and the adjacent facing portion of the bag and are removable with the bag to be peeled therefrom once and fused thermoplastic has cooled sufficiently to regain its cold strength to permit their removal without endangering the seal.

5 Claims, 4 Drawing Figures PATENTED FEB 1 8 I975 sum 2 or 2 APPARATUS FOR EVACUATING AND SEALING THERMOPLASTIC BAGS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to an apparatus for evacuating and sealing thermoplastic bags and, more particularly, to improvements in the evacuating nozzle and the bag engaging heat sealing means making the apparatus more suitable as a household appliance.

2. Description of the Prior Art Thermoplastic bag evacuating and sealing devices have become quite popular in that,'with the development of inexpensive fusible thermoplastic bags, it offers a viable alternative to preserving foodstuffs in a manner such that the foodstuff can subsequently be heated for serving without prior removal from the bag.

In the past, such bag evacuating and sealing devices were not entirely satisfactory mainly because of the tendency of the sides of the bags to collapse upon themselves almost immediately after the evacuation was begun which in turn prevented the evacuation of the air trapped generally adjacent the foodstuff. Different attempts were proposed to alleviate this tendency, such as maintaining the sides of the bags taut to prevent their collapse, shown in US Pat. No. 2,749,686, or providing specially designed plastic bags having small or minute deformations or channels extending from adjacent the nozzle to below the foodstuff in the bag, as taught in U.S. Pat. No. 3,193,982. Mostly these required additional apparatus or would work with only specially designed bags with the result that these devices never met with broad acceptance as a household appliance.

Further, the fusing of the opposing sidewalls, and thus the seal, is generally accomplished by pressing the sidewalls together between the heated bar and an opposing pressure bar. However, because of the thinfilmed wall comprising the bags, the temperature of the heater bar and the duration of the pressing step were relatively critical in that a complete fusion is required to obtain a good seal without that part of the bag contacting the heater becoming stuck thereto. Coating heater bars with a release material such as Teflon is well-known, also taught in US. Pat. No. 3,193,982,-

along with constructing bags of a laminated plastic where the interfacing walls have a lower melting point than the outer layer which contacts the heater. However, even these have not proved satisfactory for the reason that in the first instances under prolonged use even a material such as Teflon develops some adhesion between it and the thermoplastic bag. This adhesion is relatively critical in that the fused seal is easily broken when the bag is removed from the coated bars because of the extremely limited strength of the seal while still at or near its fusion temperature. And in the second instance, bags constructed of such a laminated material were relatively expensive.

SUMMARY OF THE INVENTION The bag sealing and evacuating apparatus of the present invention provides an evacuating nozzle sized to tightly engage the mouth of the bag in sealing relationship and configured so as to prevent symmetrical orientation of the bag on the nozzle. Thus, the opposing sidewalls of the bag are of different longitudinal dimension so that as they collapse together on the initiation of the evacuation, they inherently provide wrinkles which in turn provide air passageways from adjacent the foodstuff to the evacuating nozzle. Further, thin parting strips of a heat conducting material are interposed between each side of the bag and the adjacent sealing bars. The bars press against the strips which in turn DRAWING DESCRIPTION FIG. 1 is a perspective view of the bag evacuating and sealingdevice of the present invention;

FIG. 2 is a vertical cross-sectional side view thereof;

FIG. 3 is a view similar to FIG. 2 showing the device in sealing position; and,

FIG. 4 is a perspective view of the evacuating nozzle having a portion broken away.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the bag evacuating and sealing unit 10 of the present invention comprises a rectangular box-like plastic housing 12 having a substantially planar vertical front face 14 with the opposing back face defining slotted apertures for engaging screw-heads for mounting the unit on a pedestal stand (as shown in phantom) or a wall. The housing 12 generally encloses the electrically actuated components such as a small vibrating diaphragm air pump 18 (schematically illustrated in FIG. 2) of the type generally used to pump air for smaller aquariums, but in this instance utilizing the inlet side of the pump to create a subatmospheric pressure in the bag to be sealed.

The housing 12 also encloses a heater bar 20 extending horizontally substantially across the face 14 of the housing and movably mounted so as to be extended forwardly of the general plane of face 14 or retracted into i the housing 12 through an appropriately sized opening 22 in the front face 14. The heater bar, as is well known, is electrically actuated and connected in circuit with the pump 18 such that they are both energized together.

The unit 10 also includes a generally U-shaped handle member 24, with the free ends 26 of the U supported on inwardly extending hinge portions 27 that project into the housing to provide an enclosed hinge attachment and further utilized to control an internal switch (not shown) which energizes the circuit in response to the upper position of the handle as shown in FIG. I. The lower portion 28 of the handle 24 is substantially horizontal throughout its length and includes a rearwardly facing channel 30 for receipt of a resilient pressure pad member 32 that, when the handle is pivoted to its operative lower pressure position, is in substantial alignment with the heater bar 20 throughout its entire length. A pair of pins 34 project forwardly of the front face 14 generally above and adjacent each end respectively of the heater bar 20.

A bag engaging evacuating nozzle 36 also projects forwardly of the front face 14 and is attached thereto by a fitting 37 which also provides a conduit between the nozzle 36 and the pump inlet. A bent spring wire member 38, which is generally U-shaped, is attached to the back face of the nozzle as shownin FIG. 4 and provides two outwardly projecting spring-fingers 41.

Thermoplastic bags, such as polyethylene, for use on such an evacuation and sealing device as above described generally provide a substantially flat, rectangular envelope having heat sealed, i.e., fused, edges along the margin of the two sides and the bottom, leaving the top open. The fused edge portions generally are of a width to provide sufficient strength for the fused juncture and these marginal portions, at least along the sides, oftentimes include apertures for the purpose of engaging bag retaining pins on such apparatus as just described.

In principle, the bag evacuating and sealing unit above described would operate as follows:

Once the foodstuff to be preserved is placed within the bag, as shown in FIG. 1, the open mouth of the bag is sleeved over the bag engaging evacuating nozzle and retained there to effect a substantially sealed engagement between the nozzle and the bag by positive retaining means such as fingers 41 engaging the apertures in the side fused margins. Withthe handle 24 in the raised position shown in FIG. 1, both the pump 18 and the heater bar 20 would be energized. Once the pump had evacuated the air from the bag, the heater bar would be at its operational temperature, sufficient to fuse the polyethylene sidewalls of the bag together. The handle would then be lowered to press the neck of the bag (i.e., that portion just below the nozzle) between the pressure bar 32 and the heater bar. Rotating the handle, in addition to extending the heater bar forwardly of the front face, would deenergize the heater, leaving the heat retained in the bar available to fuse the sidewalls of the bag together, but preventing overheating the bar when it was engaging the bag and thereby pre-. venting completely fusing the bag onto the bar 20. In the start or at rest position, the handle would remain down so that the unit would be deenergized.

Without more, the bag evacuating and sealing unit as described would have the same two disadvantages discussed in the prior art in that because the opposed walls of the bag were relatively close and their thin-walled construction provides great flexibility, once the vacuum was initiated, the walls had an inherent tendency to collapse together in the neck area, which, when once accomplished, blocked any further evacuation of the air adjacent the foodstuff. Also, no matter at which temperature the heater bar was operated, it had to be sufficient to fuse the opposite walls together which inherently would cause some adhesion also between the heater bar and the adjacent wall of the bag. If rapid operation were not required, the bag could remain on the device and undisturbed until sufficient cooling had solidified the semi-fluid fused seam and the bag could then be removed from the heater; however, care had to be taken because if the bag were removed from the bar before the seam had regained its cold strength, the integrity of the seam could be easily destroyed through the force required to unstick the plastic from the bar being sufficient to part the still soft seal.

The present invention is concerned with specific structure for such a bag evacuating and sealing unit for eliminating these disadvantages. First, it will be noted with specific reference to FIGS. 1 and 4, the bag engaging nozzle 36 is non-symmetrical about any major axis as viewed in a plane generally perpendicular to the bag engaging side walls, and in fact, has an arcuate front face 36a with a planar back face 36b forming, in horizontal cross-section, an elliptical segment having rather sharp corner junctures at the ends. Also, the front face 36a is tapered inwardly downwardly, as are the corners, so that as the bag is sleeved over the nozzle, the perimeter of the engaging portion of the nozzle gradually increases to effect a tight engagement between the nozzle and entire periphery defining the mouth of the bag.

The effect of such a nozzle which is non-symmetrical about its major dimension is to cause the oppositely facing walls of the bag, at least in the neck area immediately sub-adjacent the nozzle, to be of different horizontal dimension, i.e., the flat rear portion is in opposing facing relationship with the front arcuate portion, with the arcuate length necessarily greater than the flat length. Therefore, when the opposed facing walls of the bag collapse against one another during evacuation of the air, this differential in their length inherently causes wrinkling of the front wall of the bag and these wrinkles in turn provide air passage spaces between the volume of the bag adjacent the foodstuff and the nozzle and prevent the collapsed walls from completely blocking further evacuation of the bag. Further, these wrinkles are of such a limited height that they do not effect ability of the bars to complete the seal in any way when the bag is pressed between the heater bar 20 and the pressure bar 32.

The device of the present invention further includes parting strips 44 which are elongated strips of a material that has a higher fusion temperature than the thermoplastic bag and are relatively thin so as to have a minimal heat mass. The strips in the preferred embodiment are made of Teflon and include apertures at their opposite ends in alignment with the pins 34 on the front face of the unit. The strips are also of a sufficient height to extend downwardly to pass the heater bar. In practice, and as shown in FIG. 1, the bag is sandwiched between opposing parting strips 44 and the strips are disposed such that they are interposed between the heater bar and the pressure bar. Thus, when the bag is evacuated and the heaterbar is at its operational elevated temperature, the handle is rotated downwardly to press the strips and bag against the heater bar as is shown in FIG. 3. The strips are sufficiently thin so that the heat of the baris rapidly conducted through the immediate strip to the bag whereupon fusion between the facing surfaces of the bag effects a seal. Once the seal is made (by momentarily holding the handle 24 in a presseddown position), the handle can be released and placed again in an elevated position where it energizes the heater without any concern of adhesion between the pressure bar 32 and the bag or the heater bar 20 and the bag as the parting strips 44 remain against the bag. In this way, the bag and both parting strips can be removed as a unit and the strips 44 allowed to cool before removal from the bag. Another pair of parting strips can then be placed in position for the next sealing operation without the user being required to wait for the initially used parting strips to cool; however, as the parting strips are relatively thin, there is retained in them a minimal amount of heat and they cool quite rapidly, thus permitting the fused seal to solidify and regain its strength for removal of the parting strips 44 in time to be used at least in the next subsequent sealing operation.

For ease of maintaining the strips in proper aligned position, the opposing strips in the preferred embodiment were in fact opposing legs of a hair-pin bent Teflon strip so that the parting strips formed a unitary piece. Further, although Teflon strips were used, other material such as Mylar, aluminum foil, etc., can be used as long as whatever material is chosed has a melting point higher than the operating temperature of the heater bar to prevent any adhesion between these abutting facing surfaces.

Thus, a bag evacuating and sealing unit is shown, which because of the nozzle configuration, causes the bag to collapse in a manner that inherently provides wrinkles that act as air passages so the bag can be completely evacuated and, with the use of parting strips which are removable with the bag, eliminates adhesion between the heating element on the device and the thermoplastic bags and transfers any adhesive force to parting strips that can remain with the bag when the bag is removed from the device, until the seal has regained its cool strength and then removed for reuse.

We claim:

1. In an apparatus for evacuating air from a thermoplastic bag and subsequently sealing the mouth of said bag comprising:

evacuating means including a nozzle in fluid communication with a vacuum pump, said nozzle having spacially separated opposing walls joined at their ends to define a periphery for substantially air-tight engagement with the internal extent of said mouth; means for fusing opposing sidewalls of said bag together in sealing engagement to prevent leakage of air through said mouth, said fusing means including an electrically heated bar extending across and facing one wall of said bag and an opposing pressure bar extending across and facing the other wall of zle and a second position pressing the bag therebetween sub-adjacent said nozzle; and means interposed between said named bars and the respective adjacent wall of said bag to facilitate parting said fused portion of said bag from said fusing means wherein the improvement comprises:

said nozzle having a mouth engaging periphery describing a profile which is asymmetrial about any axis parallel to its major dimension, said nozzle further being tapered inwardly whereby said periphery thereof increases in the direction of moving said bag into said air-tight engagement.

2. Structure according to claim 1 wherein the portion of the periphery of said nozzle engaging said one of said sidewalls of said bag is greater than the portion of the periphery of said nozzle engaging the other of said sidewalls.

3. Structure according to claim 2 wherein one of said walls of said nozzle defines an arcuate peripheral portion and the other of said walls of said nozzle defines a substantially planar peripheral portion.

4. Structure according to claim 1 wherein said parting means comprises a thin walled sheet of heat trans ferable material removably mounted adjacent each wall of said bag and moveable into a pressing relationship with said bag when pressed between said named bars.

5. Structure according to claim 4 wherein said material has a higher fusion temperature then the operating temperature of said heater bar. 

1. In an apparatus for evacuating air from a thermoplastic bag and subsequently sealing the mouth of said bag comprising: evacuating means including a nozzle in fluid communication with a vacuum pump, said nozzle having spacially separated opposing walls joined at their ends to define a periphery for substantially air-tight engagement with the internal extent of said mouth; means for fusing opposing sidewalls of said bag together in sealing engagement to prevent leakage of air through said mouth, said fusing means including an electrically heated bar extending across and facing one wall of said bag and an opposing pressure bar extending across and facing the other wall of said bag, said two named bars being mounted for relative movement between a first position permitting the bag to be placed therebetween on said nozzle and a second position pressing the bag therebetween sub-adjacent said nozzle; and means interposed between said named bars and the respective adjacent wall of said bag to facilitate parting said fused portion of said bag from said fusing means wherein the improvement comprises: said nozzle having a mouth engaging periphery describing a profile which is asymmetrial about any axis parallel to its major dimension, said nozzle further being tapered inwardly whereby said periphery thereof increases in the direction of moving said bag into said air-tight engagement.
 2. Structure according to claim 1 wherein the portion of the periphery of said nozzle engaging said one of said sidewalls of said bag is greater than the portion of the periphery of said nozzle engaging the other of said sidewalls.
 3. Structure according to claim 2 wherein one of said walls of said nozzle defines an arcuate peripheral portion and the other of said walls of said nozzle defines a substantially planar peripheral portion.
 4. Structure according to claim 1 wherein said parting means comprises a thin walled sheet of heat transferable material removably mounted adjacent each wall of said bag and moveable into a pressing relationship with said bag when pressed between said named bars.
 5. Structure according to claim 4 wherein said material has a higher fusion temperature then the operating temperature of said heater bar. 